The Program will continue as an interinstitutional interdisciplinary program in studies of the pathophysiology of thrombosis and atherosclerosis with consideration also of allied problems of the circulation. In this, the final year of the current budget period, the Program will include in addition to studies directly related to thrombosis, an inquiry into servo mechanisms in the failing heart, nonrenin related forms of hypertension, and metabolism of catecholamines in the lung. Other studies will include basic studies of platelet activation, mechanisms of interaction of blood elements with the vessel wall and warfarin-induced changes in prothrombin and related compounds.